8/13/2019 DSP Lab 4-Handout Modified

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Department of Telecommunication Engineering,

Mehran University of Engineering & Technology

Digital Signal Processing Lab 4

(6thTerm, 09TL)

StudentsName: _________________________________ Roll no: _________ Group: ____

Points: _______ Date of Submission: _____________ Teachers Signature: _____________

IN-LAB ASSIGNMENT

Lab Task 1: Plot the following signals

(a) u[n-10] (b) u[n]-u[n-10] (c) u[-n+10]-u[n-10]

Lab Task 2: Plot the signal

in time-domain and frequency domain. Use f = 1

KHz, 20 KHz, 50 KHz. Verify the signal frequency content in frequency-domain

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The first part of this task requires you to create a sinusoidal signal with the given

frequencies. This is straightforward and I believe most of you were already able to do this.

One problem was that, you could not really observe the signal in time-domain. But you

should have expected it, since the frequency is too high, you have more than 2000 samples

for f = 1 KHz, in a second. It is difficult to observe the signal with so many samples in time-

domain (entire plot gets filled up with blue colour!), but, you can select a few samples and

observe it. Check out this code.

% Matlab Code for f = 1 KHz

f = 1e3; % 1KHz frequencyfs = 3*f; % sampling frequency, greater than Nyquist's rateT = 1/fs; % sampling instantn = 0:T:5; % time vector, using step equal to sampling instanty = -sin(2*pi*f*n); % sinusoidstem(n(1:100),y(1:100)) % small number of samples being plotted% If you can't observe the sinusoid, replace stem by plotfigure,plot(n(1:100),y(1:100))

Now, the next part, to represent this signal in frequency domain, using the user definedfunction dtft.m However, the default function which you would have copied from Lab

Handout 3, only has a frequency range from -10 to 10 Hz. Obviously, using the original

function to view the 1 KHz signal in frequency domain wont give accurate results. Therefore,

you need to modify it.

The simple modification is to change the frequency range from -10 Hz : 10 Hz to something

suitable. In our case, it can be -5 KHz : 100 : 5KHz (Whats the 100 for?)

Now you can use this function for frequency domain analysis. Be advised, if you dont have

a powerful processor, youd better skip the 50 KHz signal

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8/13/2019 DSP Lab 4-Handout Modified

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Department of Telecommunication Engineering,

Mehran University of Engineering & Technology

Lab Task 4: Write a Matlab program to find the impulse and the step responses of the

systems described by the following difference equations

(a) y[n] + 0.7y[n-1]

0.45y[n-2]

0.6 y[n-3] = 0.8x[n]

0.44x[n-1] + 0.36x[n-2] + 0.02x[n-3]

(b) [ ] Lab Task 5:Find the convolution sum of the following pair of sequences

(a) { { (b)

{

Organize your Matlab Programs, Plots and Submit them